542 INDEX TO THE STKATIGEAPHY OF NOKTH AMERICA. 



and basalt. The more acid dikes are apparently characteristic of the Triassic rocks and were 

 intruded soon after the folding which must have closely followed Triassic time, for they do 

 not cut the younger rocks. * * * 



The Triassic fauna of the region as now known is almost limited to the single species 

 Psevdomonotis suhcircularis Gabb, which is very abundant in certain layers of shale and lime- 

 stone at Bear Cove and Cold Bay. Specimens from the latter locality were described and 

 figured by Fischer as Monotis salinaria, which it resembles in its general features, but a com- 

 parison of a large series of specimens from Alaska with a similar series of Gabb's Cahfornia 

 species shows that tlrey are not separable. The species belongs to the group of Pseudomonotis 

 ochotica, which is characteristic of the Upper Triassic of Siberia and the boreal regions generally. 



In Cahfornia Pseudomonotis suhcircularis is confined to the Swearinger slates, which form 

 the uppermost Triassic formation of that region. Similar beds with the same fossil occur in 

 Vancouver and Queen Charlotte islands and on the mainland of British Columbia, and they 

 cover considerable areas in the Copper River region of Alaska. 



At Bear Bay the much-folded Triassic hmestone yielded imperfect specimens of a Halobia, 

 and at Cold Bay a few imperfect ammonites not generically determined were obtained in beds 

 overlying the Pseudomonotis layers, but possibly still within the Triassic. 



O 7-8. SOUTHEASTERN ALASKA. 



The first determination of Triassic in Alaska was made by Paul Fischer ^^° 

 in 1872. Rocks of this age in the Mount St. Elias Range are also described by 

 C. W. Hayes.*^^ Referring to the "Vancouver series/' Brooks"'^ says: 



It is to be expected that this Triassic series will be found in the adjacent parts of Alaska, 

 but up to the present time it has not been positively identified. It has been shown that certain 

 metamorphic terranes carry Permian fossils, and it is quite possible that the Triassic beds may 

 be infolded with these, as is the case with the Carboniferous of Queen Charlotte Islands. This 

 view is borne out by some obscure fossils (probably Mesozoic) which have recently been found 

 by Prindle near Fort WrangeU. While reconnoitering the southern part of the Alexander 

 Archipelago a succession of conglomerates, black shales, and slates was encountered and called 

 the Gravina series, from the name of the island where they occur. These rocks are closely 

 infolded with the Vallenar series (Devonian), but the two formations are probably separated 

 by an unconformity. So little was learned of the distribution and structural relations of this 

 horizon that the wisdom of giving it a distinct name now seems open to question. The Gravina 

 was correlated with Dawson's Queen Charlotte group (Cretaceous), but on reviewing the evi- 

 dence its identity with the Vancouver series (Triassic) seems equally probable. In 1904 Wright 

 found a conglomerate and slate series on Admiralty Island which yielded Lower Cretaceous 

 or Jurassic forms. 



In the same insular region there are large areas of massive, basic igneous rocks, chiefly of 

 eflPusive origin, which were grouped together under the name Kasaan greenstone and were pro- 

 visionally assigned to the Mesozoic. On the Queen Charlotte Islands, to the south, rocks of a 

 similar character occur in both the Triassic and in the Cretaceous, and the Kasaan effusives may 

 belong to either period, but in the report cited were provisionally placed in the Cretaceous and 

 correlated with the rocks of the Queen Charlotte group. 



O 9. DBASE AND LIARD BIVEBS, BRITISH COLUMBIA. 



Certain strata, " consisting of regularly bedded, dark, calcareous, flaggy argil- 

 lites, alternating with gray flaggy and massive limestones" were observed "at the 

 second great bend" of the Dease in 1887 by Dawson, ^^^* who notes their lithologic 

 resemblance to the " Triassic of the west coast" but, not having found fossils, regards 

 the evidence as " too imperfect for a reference of the beds." 



